95 research outputs found
mohller/AstroPhoMes: AstroPhoMes v0.4
No full textThe code has been updated to reflect the state of the paper L. Morejon et al 2019 at the moment it was accepted for publication.
Changes from previous version:
Corrected in EmpiricalModel class the pion inclusive cross section treatment for energies above 1 GeV (see paper)
Included a test to evaluate the correctness of the implementation
Modifications to the Howto_example.ipynb notebook to be consistent with the rest of the changes
Further testing is ongoing..
AstroPhoMes: Photomeson models for UHECR interactions with photons
No full text<p>This is a code to calculate cross sections for photohadronic interactions in the photomeson regime. It is intended to be used in the simulation of sources and transport of Ultra-High Energy Cosmic Rays and the related production of neutrinos and secondary nuclei.</p>
New Interaction Models of Ultra-high-energy Cosmic Rays from a Nuclear Physics Approach
No full textDer Ursprung der ultrahochenergetischen kosmischen Strahlung (UHECRs) benötigt Modelle der photonuklearen kosmischen Strahlungsinteraktionen. In dieser Arbeit stelle ich Modelle vor, die drei Aspekte der Modellierung der Hochenergie-Astronuklearphysik verbessern: die Photomesonenproduktion durch Kerne der kosmischen Strahlung, die schwerer als Protonen sind, die Gammastrahlenemission von instabilen Kernen, die durch den Photodisintegrationsprozess der kosmischen Strahlung erzeugt werden, und die Simulation der extragalaktischen Ausbreitung von Kernen, die schwerer als Eisen sind (sogenannte superschwere Isotope). Das Photomesonenmodell ist das erste in der Literatur, das über das einfache Prinzip der Nukleonen-Superposition hinausgeht. Es liefert eine detailliertere Beschreibung der inelastischen Wirkungsquerschnitte und des emittierten Spektrums von Sekundärteilchen, einschließlich Isotopen und Pionen, die zu Photonen und Neutrinos führen. Die Auswirkungen des Modells werden in Simulationen von Gammastrahlenausbrüchen und Gezeitenstörungsereignissen gezeigt, und es beeinflusst signifikant die hochenergetische Neutrinoemission, die chemische Zusammensetzung und das Spektrum der emittierten UHECRs. Das zweite Modell beschreibt die Photoproduktion aus den De-Exzitationen und Zerfällen instabiler Kerne, die aus dem Photozerfall der kosmischen Strahlung in Wechselwirkung mit astrophysikalischen Photonen resultieren sollen. Ihre Wirkung wird am Photoemissionsspektrum des Kerns von Centaurus A veranschaulicht und mit ähnlichen Arbeiten verglichen, mit denen es Unstimmigkeiten gibt. Schließlich wird der Photodesintegration von UHECR überschweren Kernen diskutiert. Eine Wechselwirkungstabelle wird unter Verwendung von Querschnitten aus TALYS konstruiert, und die Wechselwirkungsraten werden im Zusammenhang mit der extragalaktischen Ausbreitung berechnet. Überschwere Kerne breiten sich in bestimmten Energiebereichen weiter aus als leichtere Kerne.The origin of the ultra-high-energy cosmic rays (UHECRs) is still unknown. Photonuclear interactions of cosmic rays are key to understanding this problem in a multimessenger context. Nuclear physics insights are crucial in building accurate models to interpret the data that indicates UHECR can be heavier than protons. This thesis presents models that improve three aspects of high-energy astronuclear physics modelling: photomeson production by cosmic-ray nuclei heavier than protons, gamma-ray emission from unstable nuclei created by the photodisintegration of cosmic rays, and the simulation of extragalactic propagation of nuclei heavier than iron (so-called superheavy isotopes). The photomeson model is the first in the literature to go beyond the simple principle of nucleon superposition. It provides a more accurate description of the inelastic cross sections, and the emitted spectrum of secondary particles, including isotopes and pions which lead to photons and neutrinos.The model’s impact is shown in simulations of gamma-ray bursts and tidal disruption events, and it affects significantly the high-energy neutrino emission, the chemical composition and the spectrum of the emitted UHECRs. The second model describes photoproduction from de-excitations and decay of unstable nuclei, which are expected to be produced in photo-disintegration of cosmic rays interacting with astrophysical photons. Its impact is illustrated in the photo-emission from the core of the Centaurus A and compared to similar works with which is in disagreement. This supports the need for sufficiently accurate models. Lastly, the photodisintegration of UHECR superheavy nuclei is discussed. An interaction table is produced with cross sections obtained from TALYS and the interaction rates computed in the context of extragalactic propagation. Superheavy nuclei propagate further than lighter nuclei in certain energy ranges. The models developed are publicly available as open-source software
mohller/AstroPhoMes: AstroPhoMes v0.2
No full text<p>Release for production, with updates on file structure, license and readme files.</p>
Numerical studies of a layered lithium-boron target for laser-driven aneutronic fusion reactions
No full textThis paper explores a novel target design for laser-driven, aneutronic, proton-boron and proton-lithium fusion reactions consisting of a stack of boron and lithium foils. In contrast to a homogeneous target, this multi-layer setup provides additional fusion channels in the different materials. The composition of the layers is chosen in descending order of the fusion reactions\u27 thresholds, facilitating the fusion of protons that penetrate further into the material despite their energy losses due to electronic and nuclear stopping power. We employ a combination of Fluka simulations and additional numerical computations to evaluate thousands of target configurations. Four different beam energy distributions are considered: two Gaussian distributions with 6~MeV and 10~MeV mean energies, respectively, a Maxwell-Boltzmann distribution and a power law distribution. We explore the production of energy in a range of layer thicknesses motivated by the proton ranges based on ionization losses. The configuration which maximizes the produced energy for each beam type is reported. The production of fusion energy ranges from hundreds to thousands of millijoules for proton bunches of having mean energies between 2-10 MeV
English as a Lingua Franca in Europe and Asia: teaching policy on the ground
No full textThe present thesis considers the topic of English as a Lingua Franca as it is perceived and experienced by three groups: the ELF research community, ELT professionals, and ELF users themselves. This thesis first presents an overview of the theoretical foundations of ELF research, identifying key topics with which the ELF research community has grappled in recent decades. In order to determine how much closer the ELT community has gotten to aligning teaching policy, practices, and goals to students' specific needs and expectations, sociolinguistic research in the form of seven semi-structured interviews was conducted with L2 English speakers who use ELF to live, work, and study in their daily lives, and the ELT professionals tasked with developing their English skills in the classroom. The content of these interviews is then analyzed with regard to the specific needs and expectations of ELF users and the concerns of ELT professionals, followed by a discussion of the key issues uncovered in these interviews in light of the theoretical background of ELF research. The author provides suggestions for further research aimed at improving the ELT community's role in developing ELF proficiency in the expanding circle. Keywords: English as a Lingua Franca, English Language Teaching, Expanding Circle, ELF..
Astrophysical neutrino production and impact of associated uncertainties in photo-hadronic interactions of UHECRs
No full textHigh energy neutrinos can be produced by interactions of ultra-high energy cosmic rays (UHECRs) in the dense radiation fields of their sources as well as off the cosmic backgrounds when they propagate through the universe. Multi-messenger interpretations of current measurements deeply rely on the understanding of these interactions. In order to efficiently produce neutrinos in the sources of UHECRs, at least a moderate level of interactions is needed, which means that a nuclear cascade develops if nuclei are involved. On the other hand, the available cross-section data and interaction models turn out to make poor predictions for most nuclei heavier than protons. We show the impact of these uncertainties in state-of-the-art photo-disintegration models and motivate nuclear cross-section measurements. Further, we discuss extensions for photo-meson models currently used in astrophysics and demonstrate the importance of understanding the details of UHECR interaction with the Glashow resonance
Astrophysical neutrino production and impact of associated uncertainties in photo-hadronic interactions of UHECRs
No full textHigh energy neutrinos can be produced by interactions of ultra-high energy cosmic rays (UHECRs) in the dense radiation fields of their sources as well as off the cosmic backgrounds when they propagate through the universe. Multi-messenger interpretations of current measurements deeply rely on the understanding of these interactions. In order to efficiently produce neutrinos in the sources of UHECRs, at least a moderate level of interactions is needed, which means that a nuclear cascade develops if nuclei are involved. On the other hand, the available cross-section data and interaction models turn out to make poor predictions for most nuclei heavier than protons. We show the impact of these uncertainties in state-of-the-art photo-disintegration models and motivate nuclear cross-section measurements. Further, we discuss extensions for photo-meson models currently used in astrophysics and demonstrate the importance of understanding the details of UHECR interaction with the Glashow resonance
Angličtina jako lingua franca v Evropě a v Asii: Výuková politika v praxi.
No full textThe present thesis considers the topic of English as a Lingua Franca as it is perceived and experienced by three groups: the ELF research community, ELT professionals, and ELF users themselves. This thesis first presents an overview of the theoretical foundations of ELF research, identifying key topics with which the ELF research community has grappled in recent decades. In order to determine how much closer the ELT community has gotten to aligning teaching policy, practices, and goals to students' specific needs and expectations, sociolinguistic research in the form of seven semi-structured interviews was conducted with L2 English speakers who use ELF to live, work, and study in their daily lives, and the ELT professionals tasked with developing their English skills in the classroom. The content of these interviews is then analyzed with regard to the specific needs and expectations of ELF users and the concerns of ELT professionals, followed by a discussion of the key issues uncovered in these interviews in light of the theoretical background of ELF research. The author provides suggestions for further research aimed at improving the ELT community's role in developing ELF proficiency in the expanding circle. Keywords: English as a Lingua Franca, English Language Teaching, Expanding Circle, ELF...Diplomová práce se zabývá otázkou, jak angličtinu jako lingua franca (ELF) vnímají tři skupiny: výzkumníci zabývající se ELF, vyučující angličtiny (ELT) a samotní uživatelé ELF. V práci jsou nejprve představena teoretická východiska výzkumu ELF a identifikována hlavní témata, kterým se toto odvětví bádání věnuje v posledních dekádách. Aby bylo možné určit, zda se odborníkům zabývajícím se ELT daří propojit plánování, praxi a cíle výuky se specifickými potřebami a očekáváními studentů, bylo provedeno sociolingvistické šetření sedmi částečně strukturovanými rozhovory se mluvčími angličtiny jako L2, kteří používají ELF v každodenním životě, v práci a při studiu, a rozhovory s profesionály, kteří mají příslušné dovednosti rozvíjet ve výuce. Obsah těchto rozhovorů je následně analyzován s ohledem na specifické potřeby a očekávání uživatelů ELF a zájmů a cílů učitelů jazyka. Následuje vyhodnocení hlavních témat, která vyvstala během těchto rozhovorů, a jejich porovnání s teoretickým výzkumem v oblasti ELF. Autorka navrhuje další směr výzkumu s cílem zlepšit roli učitelů a ostatních profesionálů v oblasti ELT při rozvíjení dovedností potřebných pro komunikaci v tzv. rozšiřujícím se kruhu. Klíčová slova: angličtina jako lingua franca, výuka angličtiny, rozšiřující se kruh, uživatelé ELF, odborníci na ELTÚstav anglického jazyka a didaktikyDepartment of the English Language and ELT MethodologyFilozofická fakultaFaculty of Art
Propagation of Ultra High-Energy Cosmic Rays in light of the latest EBL constraints
No full textInternational audienceRecent progress in measurements and modeling of the Extragalactic Background Light (EBL) has placed considerable constraints on its spectral density. These constraints are particularly relevant for the propagation of Ultra-High Energy Cosmic Rays (UHECRs), as in the past the EBL uncertainties have significantly impacted the result of simulations that aim at inferring source properties from the observed UHECR spectral and composition data. In this contribution, we show that the reduction in EBL uncertainties recently achieved makes their impact on the propagation of UHECRs subdominant
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